1. Field of the Invention
The present invention relates to an optical-electrical transmission connector, an optical-electrical transmission device and an electronic device suitably applicable when communication between one device and the other device is performed by optical transmission.
2. Description of the Related Art
Signal transmission between semiconductor chips such as LSIs (Large-Scale Integrations) has been heretofore performed by electrical signals through a board interconnection. However, a necessary data exchange amount between semiconductor chips has pronouncedly increased with a recent increase in the functionality of MPUs (Micro Processing Units), thereby as a result various high-frequency issues occur.
Typical examples of the issues include RC (Register and Capacitor) signal delay, impedance mismatching, EMC (Electro Magnetic Compatibility)/EMI (Electro Magnetic Interference), crosstalk and the like. To overcome such issues, measures such as the optimization of interconnection arrangement, the development of new materials have been taken in related arts.
However, in recent years, effects by the optimization of interconnection arrangement, the development of new materials and the like have been hampered by physical limitations, and to achieve higher functionality of a system, it is necessary to reconsider a board configuration designed for simple mounting of semiconductor chips. For example, fine-pitch interconnection coupling by formation of a multichip module (MCM), electrical interconnection coupling by two-dimensional sealing and integration of various semiconductor chips and three-dimensional coupling of semiconductor chips which will be briefly described below have been developed.
Fine-Pitch Interconnection Coupling by Formation of a MCM
High-performance chips are mounted on a mounting board made of ceramic, silicon or the like, and the high-performance chips are coupled by fine-pitch interconnection. The coupling method allows a reduction in an interconnection pitch, thereby a data exchange amount is able to be remarkably increased by increasing a bus width.
Electrical Interconnection Coupling by Two-Dimensional Sealing and Integration of Various Semiconductor Chips
Various semiconductor chips are two-dimensionally sealed and integrated by using a polyimide resin or the like, and the semiconductor chips are coupled on such an integrated board by fine-pitch interconnection. The coupling method allows a reduction in an interconnection pitch, thereby a data exchange amount is able to be remarkably increased by increasing a bus width.
Three-Dimensional Coupling of Semiconductor Chips
Through electrodes are arranged on various semiconductor chips, and the semiconductor chips are bonded together to form a laminate configuration. Connection between semiconductor chips of different kinds is physically shortened by the interconnection method, so that issues such as signal delay are able to be avoided. However, it is necessary to consider an increase in a heating value caused by laminating the semiconductor chips, a thermal stress between the semiconductor chips, and the like.
Moreover, to achieve higher-speed and larger-capacity signal exchange, optical transmission and coupling techniques by optical interconnection has been developed (for example, refer to Nikkei Electronics, “Encounter with optical interconnections”, Dec. 3, 2001, p. 122-125, and NTT R&D, vol. 48, no. 3, p. 271-280 (1999)). When signal transmission between semiconductor chips is performed by optical signals, the issue of RC delay which arises in electrical interconnection is prevented, and the transmission speed is able to be remarkably improved. Further, when signal transmission between the semiconductor chips is performed by optical signals, it is not necessary to take measures against electromagnetic waves, thereby interconnection is able to be designed relatively freely.
Techniques of optical interconnection between semiconductor chips include various systems. Examples of the systems include an active interposer system, a free-space transmission system, an optical connector connection system, a light guide embedding system, a surface mounting system and the like which will be briefly described below.
Active Interposer System (refer to Nikkei Electronics, “Encounter with Optical Interconnections”, Dec. 3, 2001, p. 125)
This is a system of propagating signals to a light guide mounted on a board interconnection. A photonic device such as a light-emitting device or a light-sensing device is mounted on a back surface of a transceiver module arranged on the board interconnection with a predetermined gap in between, and the photonic device is precisely positioned with respect to a 45° total reflection mirror of the light guide. The system has an advantage that the system is laid out on the mounting configuration of an existing board interconnection.
Free-Space Transmission System (refer to Nikkei Electronics, “Encounter with Optical Interconnections”, Dec. 3, 2001, p. 123)
This is a system of propagating signals by mounting an optical interconnection board (quartz) on a back surface of a board interconnection, and reflecting light zigzag in the optical interconnection board. When photonic devices are arranged into an array, and signals are transmitted in a free space in the optical interconnection board, the number of channels is able to be increased to a few thousand channels in principle. Moreover, to make optical axis alignment easier, a hybrid optical system including a combination of a few lenses is formed. The system has advantages that multiplexing transmission of a few thousand channels is able to be performed in principle, and optical axis alignment is easily performed because of the hybrid optical system.
Optical Connector Connection System (refer to Nikkei Electronics, “Encounter with Optical Interconnections”, Dec. 3, 2001, p. 122)
This is a system capable of freely setting a light guide after arranging an optical connector around a semiconductor chip, and mounting the semiconductor chip. The system has advantages that an optical axis alignment step of which the cost is high is not necessary because precision is secured by the optical connector, an optical fiber is used as a light guide, thereby intermediate-range transmission between interconnection boards or the like is able to be performed, and the system is able to be used on the mounting configuration of an existing interconnection board.
Light Guide Embedding System (refer to Nikkei Electronics, “Encounter with Optical Interconnections”, Dec. 3, 2001, p. 124)
This is a system of directly bonding a photonic device to a back surface of a semiconductor chip, and embedding a light guide in an interconnection board. While the form of the mounting configuration of an existing interconnection board is maintained, an optical interconnection is able to be arranged. In this system, a microlens is used for optical path coupling, and the allowable amount of optical axis misalignment is able to be increased to a general mounting precision level. The system has advantages that an electrical interconnection path between the semiconductor chip and the photonic device is able to be minimized, and optical axis alignment is performed with general mounting precision by coupling of collimated light.
Surface Mounting System (refer to NTT R&D, vol. 48, no. 3, p. 271-280 (1999))
This is a system of directly bonding a photonic device on a back surface of a semiconductor chip, and directly mounting a light guide on an interconnection board. While the configuration of an existing interconnection board is maintained as it is, an optical interconnection is able to be also arranged. The system has advantages that an electrical interconnection path between the semiconductor chip and the photonic device is minimized because the photonic device is directly mounted on the back surface of the semiconductor chip, the configuration is simple, costs are able to be reduced, and the system is able to be laid out on the mounting configuration of an existing interconnection board.